This invention relates to a method for cleaning with high pressure an evaporator of that type which comprises an upstanding, round, closed vessel, at least two substantially horizontal perforated partitions which divide said vessel into an uppermost space, at least one middle space, and a lowermost space, a supply line for the liquid to be evaporated which line opens on the uppermost space, an access to said uppermost space which access is provided in the vessel wall and is closable with a cover, an access to said middle space which access is provided in the vessel wall and is closable with a cover, a discharge line for the vapour and possibly some liquid, which line opens on the lowermost space, an outlet which is provided in the vessel bottom, and an access to said lowermost space which access is provided in the vessel bottom and is closable with a cover.
Evaporators of the above-defined type are used in nuclear power stations for treating all of the leak water which is considered as possibly containing radio-active particles.
Such evaporators are notably marketed by the French Company "Stein Industrie" from Velizy Villacoublay.
Leak water which might possibly contain radio-active particles, is first pre-heated in a heater, and thereafter fed at the top to the evaporator of the above-defined type. Inside said evaporator, said leak water first flows through a separating filter and then in counter-current with added steam, through a number, generally three, horizontal perforated partitions. The major portion of the leak water evaporates and the possible radio-active particles which are not retained by the filter, remain after the evaporating. The vapour being formed is then condensated inside a condensor into water with a substantially lower radio-active degree of contamination as the original leak water.
A large portion of those radio-active particles which remain inside the evaporator collect at the bottom of the vessel and are discharged through the outlet in the vessel bottom. A portion of radio-active particles does however remain in the lime settling which, as in every evaporator, occurs on the inner side of the vessel.
Due to such lime settling or deposit, the small holes in the perforated partitions are progressively sealed, so that after some time, the good operation of the evaporator is hampered.
In the known evaporators, no special provisions are made to oppose such sealing of the small holes in the perforated partitions, nor to remove the lime deposit, so that cleaning of the spaces inside the evaporator is required from time to time.
Such cleaning which has to occur through those existing accesses which are closed with a cover during the normal working of the evaporator, to the spaces, does bring particular problems due to the lack of space around the evaporator and mostly due to the fact that such evaporator has a strong radio-active contamination.
The cleaning has thus to be made by a worker who bears protective clothing from outside the evaporator, in as simple, fast and effective way as possible.
The invention has for object to provide such a method for cleaning with high pressure an evaporator of the above-defined type, which method allows, in spite of the difficult accessibility of the evaporator inner spaces, to clean very efficiently said inner spaces in a fast and simple way.